1. Field of the Invention
The preferred embodiments of the invention are directed to the field of power generation.
2. Description of the Related Art
Generators harnessing energy from a fluid flow (such as air) are known within the art, however such generators typically have turbines or propellers which have a large cross-section. The movement of the medium creates a motive force upon the turbine or propeller, which is connected to a device to convert the movement into electricity. But the large cross-sections of these traditional designs increase the amount of wind resistance presented by the generators, limiting the practicality of their application in certain fields.
For example, the prior art describes a vehicle having a wind tunnel and turbine generator, but the aerodynamic limitations of the turbine are not ideal for vehicular applications. Those disclosures created wind resistances which would substantially decrease fuel efficiency. The energy would also be capped at a theoretical 60% recovery, further impacting the efficiency relative to the burden on the system from the design. Other generator designs have been developed to try to minimize the aerodynamic cost of the generators. For example, designs have sought to take advantage of the aeroelastic or flutter effect in aerodynamics by placing structures into the middle of a fluid flow. These designs have previously suggested using wings that move about one or two points or elastic membranes that are fixed at two ends. These designs cross the fluid flow, creating oscillations perpendicular to the fluid flow in the wing or membrane. The designs introduce drag and a blocking obstacle in the fluid flow and require supporting structures which greatly affect the cross-sectional aerodynamics. They also require a fixed direction of fluid flow that is perpendicular to the orientation of the long axis of the wing or membrane. The prior art describes one such design utilizing a string membrane pulled taut across two rigid structures. Similarly, the prior art describes wing generators have been presented which mount a wing across two support pillars to generate electricity from the pitch and yaw motion of the wing.
Kite generators have also been presented which transfer kite movement to a fixed base structure through a tether. These kites are typically flown at higher altitudes to harness the stronger wind forces. Similarly, there is currently interest in developing tethered autonomous flight vehicles with generators that are flown at high altitude to take advantage of the greater wind forces at altitude.
Prior devices typically required large structures and/or large motive forces, which often mean that the devices could only be operated under certain conditions or in certain locations. These devices also typically have many moving parts, which increase the need for maintenance and the potential for breakdown. These devices also face increased stresses as motive forces increased, requiring designs or use that compensated for high speed or shut down to avoid damage. Furthermore, the output from these devices varies substantially with the relative velocity of the medium, often requiring the design to compensate for velocities outside of a tolerance range.
These devices also often times require a fixed direction of flow. In order to compensate for varying directions of flow, previous devices have been rotatable with guiding panels to orient the device in the correct direction relative to the direction of flow.
Each of these designs presents its own complications and complexities, at least some of which can be alleviated by an embodiment of the present invention. For example, the aerodynamic cost from the cross-sectional shapes of many of these designs is too high for certain applications, such as in vehicular applications. Additionally, the mechanical complexities of some of the devices have been a noted concern, resulting in high cost, difficult maintenance, and overall complicated manufacturing. Other designs are unidirectional and not able to be accommodating of changing directions of fluid flow without additional rotational structures. Some of the designs are also dependent on the speed of fluid flow, with limited efficiency or effectiveness outside of a narrower range of preferred flow speeds. Some designs may even break down at excessive speeds, as has been shown in test flights of generators at altitude.
There is a need for a device that can generate electricity from relatively lower levels of motive force and provide smaller cross-sections. There is also a need for scalable, stackable devices to generate electricity in locations where traditional devices are not suitable. The increased use of electric and hybrid engine systems in vehicles has also created an increased need for ways of generating electricity to recharge batteries.
Also, given a stated desire to design turbine generators that operate at altitude under strong winds and via cables or tall supporting structures, there is a need for a device which minimizes aerodynamic complications associated with turbines and other non-aerodynamic shapes so as to more easily maintain operational altitude and minimize complications from stronger wind speeds.